1. Field of the Invention
The invention relates to a circuit arrangement for supplying a load, provided with a DC--DC converter comprising:
input terminals for connection to a DC voltage source, PA1 a circuit portion which comprises inductive means and first capacitive means and which interconnects the input terminals, PA1 a switching element which shunts the first capacitive means, PA1 a control circuit coupled to the switching element for rendering the switching element conducting and non-conducting with high frequency, PA1 a transformer comprising a primary winding and a secondary winding, which primary winding is comprised in the circuit portion, and PA1 an output circuit coupled to the secondary winding and provided with
output terminals for connection to the load, PA2 rectifying means coupled between the secondary winding and the output terminals, and PA2 second capacitive means connected between the secondary winding and the output terminals.
The invention also relates to a lighting unit.
2. Description of the Related Art
A circuit arrangement as mentioned in the opening paragraph is known from the proceedings of the "19th Annual IEEE Power Electronics Specialists Conference", 1988, vol. 1, pp. 9-17.
The known circuit arrangement comprises a multiresonant DC--DC converter. The switching element of the known DC--DC converter is rendered conducting while the voltage across the switching element is substantially zero, so that the amount of power dissipated in the switching element during operation is comparatively small. The amount of power dissipated in the rectifying means during operation is also comparatively small as a result of the multiresonant operation. A major drawback of the known circuit arrangement, however, is that the energy supplied by the switching device is transmitted to the output terminals during a comparatively short time interval in each high-frequency cycle. This has the result that a number of components of the circuit arrangement must be resistant to a comparatively high power level during this comparatively short time interval and must be correspondingly dimensioned. Another result is that the voltage across the switching element reaches a comparatively high value in each high-frequency cycle, which also has the result that the switching element must be dimensioned to deal with this.